最近在实用flinkx（flink1.4.0，slot内存大小1G，每个taskmanager配置两个slot，三台服务器组成的集群），发现在抽取mysql数据（单表1000万条，单条记录500字节左右）出现任务卡死的现象，JdbcInputFormat.java openInternal方法中 resultSet = statement.executeQuery();执行后无法返回，我按照JdbcInputFormat.java 中jdbc读取数据的方式单独写个java测试用例，jvm参数 -Xms1024m -Xmx1024m，出现oom异常，将jvm参数调大至2G即可正常运行，我怀疑是FetchSize设置没有生效，将openInternal方法中statement.setFetchSize(databaseInterface.getFetchSize());改为statement.setFetchSize(Integer.MIN_VALUE);，在1G内存下即可正常运行。
同时需要将获取descColumnTypeList的代码提前到statement.executeQuery()；之前执行，否则会抛出如下异常
java.sql.SQLException: Streaming result set com.mysql.jdbc.RowDataDynamic@6438a396 is still active. No statements may be issued when any streaming result sets are open and in use on a given connection. Ensure that you have called .close() on any active streaming result sets before attempting more queries.

附修改后的JdbcInputFormat.java 文件

/*

• Licensed to the Apache Software Foundation (ASF) under one
• or more contributor license agreements. See the NOTICE file
• distributed with this work for additional information
• regarding copyright ownership. The ASF licenses this file
• to you under the Apache License, Version 2.0 (the
• "License"); you may not use this file except in compliance
• with the License. You may obtain a copy of the License at

• http://www.apache.org/licenses/LICENSE-2.0
  

• Unless required by applicable law or agreed to in writing, software
• distributed under the License is distributed on an "AS IS" BASIS,
• WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
• See the License for the specific language governing permissions and
• limitations under the License.
  */

package com.dtstack.flinkx.rdb.inputformat;

import com.dtstack.flinkx.rdb.DatabaseInterface;
import com.dtstack.flinkx.rdb.type.TypeConverterInterface;
import com.dtstack.flinkx.rdb.util.DBUtil;
import com.dtstack.flinkx.util.ClassUtil;
import com.dtstack.flinkx.util.DateUtil;
import org.apache.flink.api.common.io.DefaultInputSplitAssigner;
import org.apache.flink.api.common.io.statistics.BaseStatistics;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.core.io.GenericInputSplit;
import org.apache.flink.core.io.InputSplit;
import org.apache.flink.core.io.InputSplitAssigner;
import org.apache.flink.metrics.Counter;
import org.apache.flink.types.Row;
import java.io.IOException;
import java.math.BigDecimal;
import java.sql.;
import java.sql.Date;
import java.util.;

import com.dtstack.flinkx.inputformat.RichInputFormat;

/**

• InputFormat for reading data from a database and generate Rows.

• Company: www.dtstack.com

• @author huyifan.zju@163.com
  */
  public class JdbcInputFormat extends RichInputFormat {

  protected static final long serialVersionUID = 1L;

  protected DatabaseInterface databaseInterface;

  protected String username;

  protected String password;

  protected String drivername;

  protected String dbURL;

  protected String queryTemplate;

  protected int resultSetType;

  protected int resultSetConcurrency;

  protected List descColumnTypeList;

  protected transient Connection dbConn;

  protected transient PreparedStatement statement;

  protected transient ResultSet resultSet;

  protected boolean hasNext;

  protected Object[][] parameterValues;

  protected int columnCount;

  protected String table;

  protected TypeConverterInterface typeConverter;

  protected List column;

  public JdbcInputFormat() {
  resultSetType = ResultSet.TYPE_FORWARD_ONLY;
  resultSetConcurrency = ResultSet.CONCUR_READ_ONLY;
  }

  @OverRide
  public void configure(Configuration configuration) {

  }

  @OverRide
  public void openInternal(InputSplit inputSplit) throws IOException {
  try {
  ClassUtil.forName(drivername, getClass().getClassLoader());
  dbConn = DBUtil.getConnection(dbURL, username, password);

       if(drivername.equalsIgnoreCase("org.postgresql.Driver")){
           dbConn.setAutoCommit(false);
       }
  
       statement = dbConn.prepareStatement(queryTemplate, resultSetType, resultSetConcurrency);
  
       //提前执行 |by lgm
       if(descColumnTypeList == null) {
           descColumnTypeList = DBUtil.analyzeTable(dbConn,databaseInterface,table,column);
       }
  
       if (inputSplit != null && parameterValues != null) {
           for (int i = 0; i < parameterValues[inputSplit.getSplitNumber()].length; i++) {
               Object param = parameterValues[inputSplit.getSplitNumber()][i];
               DBUtil.setParameterValue(param,statement,i);
           }
           if (LOG.isDebugEnabled()) {
               LOG.debug(String.format("Executing '%s' with parameters %s", queryTemplate, Arrays.deepToString(parameterValues[inputSplit.getSplitNumber()])));
           }
       }
  
  
       //statement.setFetchSize(databaseInterface.getFetchSize());
         //重新设定FetchSize |by lgm
       if(drivername.equalsIgnoreCase("mysqlreader")) {
           statement.setFetchSize(Integer.MIN_VALUE);
       }
       else {
           statement.setFetchSize(databaseInterface.getFetchSize());
       }
       statement.setQueryTimeout(databaseInterface.getQueryTimeout());
  
  
  
       resultSet = statement.executeQuery();
       hasNext = resultSet.next();
       columnCount = resultSet.getMetaData().getColumnCount();
  
  
   } catch (SQLException se) {
       throw new IllegalArgumentException("open() failed." + se.getMessage(), se);
   }
  
   LOG.info("JdbcInputFormat[" + jobName + "]open: end");
  

  }

  @OverRide
  public BaseStatistics getStatistics(BaseStatistics cachedStatistics) throws IOException {
  return cachedStatistics;
  }

  @OverRide
  public InputSplit[] createInputSplits(int minNumSplits) throws IOException {
  if (parameterValues == null) {
  return new GenericInputSplit[]{new GenericInputSplit(0, 1)};
  }
  GenericInputSplit[] ret = new GenericInputSplit[parameterValues.length];
  for (int i = 0; i < ret.length; i++) {
  ret[i] = new GenericInputSplit(i, ret.length);
  }
  return ret;
  }

  @OverRide
  public InputSplitAssigner getInputSplitAssigner(InputSplit[] inputSplits) {
  return new DefaultInputSplitAssigner(inputSplits);
  }

  @OverRide
  public boolean reachedEnd() throws IOException {
  return !hasNext;
  }

  @OverRide
  public Row nextRecordInternal(Row row) throws IOException {
  row = new Row(columnCount);
  try {
  if (!hasNext) {
  return null;
  }

       DBUtil.getRow(dbURL,row,descColumnTypeList,resultSet,typeConverter);
       //update hasNext after we've read the record
       hasNext = resultSet.next();
       return row;
   } catch (SQLException se) {
       throw new IOException("Couldn't read data - " + se.getMessage(), se);
   } catch (NullPointerException npe) {
       throw new IOException("Couldn't access resultSet", npe);
   }
  

  }

  @OverRide
  public void closeInternal() throws IOException {
  DBUtil.closeDBResources(resultSet,statement,dbConn);
  parameterValues = null;
  }

}